Paleozic Tectonic Transformation Of The North Qinling Belt In Shanxi Province

The Qinling orogenic belt is the division of geology, geochemistry, physical geography and geography between north China and south China, so it has become the focus of many geologists of the world. With the discovery new facts, our understanding of evolution of Qinling developed gradually. Beiqinling is between Shangdan Fault and Baoji-Luonan-Luanchuan Fault, it have own particularities in structure, geochemistry, physical geography and stratigraphy, on the stand of tectonic, it's the real division between north China and south China, and the key region to study the evolution of Qinling erogenic belt during later Paleozoic-early Mesozoic.On the guidance of the theory of plate tectonics and the new knowledge of continental dynamics.using method combined tectonic analysis and sedimentology, based on the characteristics of stratum composition, lithology, contact relationship, sedimentary environment as well as structural deformations to discuss the paleozoic tectonic transformation of the North Qinling belt.Tectonic analysis of Pre-Carboniferous metamorphic stratum and structural foliation dating have shown that The Qinling and its vicinities had happened an important regional tectonic event -Caledonian event, this event represents early paleozoic closure of the Qinling ocean basin and continent-continent obliquely diachronous collision, so we also could reconstruct Caledonian Qinling orogenic belt's basic tectonic framework. It's forland basin should exist between later Silurian and early Devonian, but Qinling orogenic belt has undergone multiple deformations, especially Indosinian intracontinental subductional orogenesis, extensive subduction might have made the absence of forland basin and molass formation of Caledonian orogenesis.Based on sedimentology study of lithology, stratum composition, granularity analysis sedimentary provenance analysis of Carboniferous and Permian as well as regional data, we consider that they represent a series of small faulted basins which had formed on the north Qinling mountanious region composing of Pre- Carboniferous metamorphic stratum.Based on analysises of characteristics of regional deformation and metamorphism as well as Carboniferous and Permian relict basins, think Qinling-Dabie orogenic belt might have undergone following Basin-mountain transformational process : the ocean basin developed in Silurian-early Paleozoic; ocean basin subduction began in Ordovician; Silurian-early Devonian continent-continent collision happened and the ocean basin disappeared; Carboniferous- Permian, with the strike-slip and pull-apart along the Shangdan fault, a series of small faulted basins formed on the north Qinling mountainous region composing of Pre-Carboniferous metamorphic stratum.The 416~419Ma dating result of structural foliation in Huayangchuan shear zone might indicate the main structure in Xiaoqinling should caused by Caledonian event, and subsequent structures should be mainly of movement of the fault blocks.